The present invention relates to a semi-automatic image tracing method and, more particularly, to a semi-automatic image tracing method adaptable to graphics processing devices, such as a computer-aided design (CAD) device or the like, which comprises semi-automatically tracing image points of an image data while carrying out a switching control for continuing the tracing processing by determining tracing conditions at a branch point of a tracing path as well as confirming the tracing path.
Heretofore, pictures drawn on paper have been inputted into a graphics processing system as image data by means of an image scanner or the like. The image data are then displayed on a display screen through the graphics processing system and the operator has manually inputted through a pointing device or the like by tracing the image data on the screen.
For example, Japanese Patent Unexamined Publication (kokai) No. 62-269,276/1987 discloses an interactive graphics input system in which a picture is scanned by an image scanner and once inputted into a computer as image data which in turn is displayed on a display screen while superposing center line image data on the image data, and inputting the graphics as vector data by designating the positions required for the graphics on the display screen by means of a coordinates designator.
In converting the image data into the graphics data (coordinate points data) such as vector data, for example, in the manner as described hereinabove, the center data for the center or center line of the image is first given and then necessary data such as an end point, branch point or corner point as the characteristic point of the image is selected from the center data and such necessary data is inputted. In this case, in the conventional technique, the characteristic points have been inputted while the center data is superposed on the image data on the display screen. Hence, the display screen is forced to become so complicated that the operator has failed to select necessary data in an efficient way.
Further, there has been developed a graphics processor of a type having a semi-automatical line-tracing function so arranged as to semi-automatically trace image points, decide a characteristic point of the image points and input a graphic data of the characteristic point.
When the characteristic point of the image traced in a semi-automatic fashion, such a semi-automatical line-tracing function for the graphics processor is so designed as to allow various parameters acting as control data for semi-automatically tracing to be altered with every image to be traced, such parameters including an image tracing parameter for tracing the image, a trace-result correcting parameter, and so on. However, a switch to be employed for controlling the tracing of the image is set uniformly in advance, so that the switch cannot be altered with every image. Further, the semi-automatically tracing processing employs a main view port displaying a whole tracing area for confirming a tracing process of the tracing path. Hence, the detail of the tracing path is to be confirmed by shifting display screens and enlarging the details of the tracing path.
It is to be noted, however, that when a characteristic point of the image, such as an end point, a branch point and so on, is determined and inputted as graphic data as a result of tracing the image data semi-automatically by means of the semi-automatical tracing function of the graphics processor, the conventional function is so designed as to trace the image and branch the tracing path into a branched direction uniformly defined in advance upon the detection of a branch point, for example, so that no attention is paid to the instance where the tracing path is intended to be partially branched into an exceptional direction other than the predetermined tracing branch path. Hence, the exceptional portion is required to be corrected individually after the semi-automatic tracing has been finished. Further, if the graphics or image to be traced would be too big or too complicated as compared with the display area of the view port, the detail of the tracing path cannot be confirmed because the whole area of the tracing path is displayed in order to confirm the tracing path during the tracing operation. Therefore, in order to confirm and correct the detail of the tracing path, the detail is enlarged after the tracing of the image has been done. This operation is so complicated.